1. Field of Invention
The present invention relates to means operable: i) to be interposed between the power line and the power input terminals of a three-phase induction motor, and ii) to control the frequency, magnitude and/or waveshape of the voltage provided to the power input terminals of this three-phase induction motor.
2. Elements of Prior Art
A three-phase induction motor is basically a synchronous device. However, most commonly available means for controlling its speed are based on controlling the magnitude of the current supplied to the motor, thereby attaining but a very modest degree of speed control in return for a significant reduction in motor efficiency.